Retinal function affected early in Type 1, 2 diabetes

By Shreeya Nanda, Senior medwireNews Reporter

Visual dysfunction manifests early in Type 1 and Type 2 diabetes, research shows, with functional impairment detected in patients with nonproliferative diabetic retinopathy lacking clinical signs and symptoms of diabetic macular oedema.

Researcher Giuseppe Querques (University Vita Salute San Raffaele, Milan, Italy) and team used spectral domain optical coherence tomography and microperimetry to evaluate central foveal thickness (CFT) and retinal sensitivity, respectively, in 36 eyes from the same number of patients with Type 1 (n=17) or Type 2 diabetes (n=19). The average age of patients in the former group was 36.0 years and that of the latter was 63.9 years.

The results were compared with those from two control groups, matched for age and gender, such that the control groups for the Type 1 and Type 2 cohorts had mean ages of 32.3 and 57.1 years, respectively.

Patients with diabetes had a significantly higher overall mean CFT than controls, at 246.2 µm versus 220.7 µm. The difference remained statistically significant when patients with Type 1 and Type 2 diabetes were considered separately and compared with their respective control groups, with mean CFTs of 234.5 µm versus 218.8 µm and 256.3 µm versus 222.8 µm, respectively

Overall mean retinal sensitivity was significantly lower in the diabetes compared with the control group, at 18.3 dB and 19.9 dB, respectively. Considered separately, patients with Type 1 and Type 2 diabetes had mean retinal sensitivities of 18.9 and 17.7, respectively – and again these were significantly lower than the values obtained for the younger and older control groups, at 19.9 and 19.8, respectively.

Further analysis showed that presence of systemic hypertension and poor glycaemic control adversely affected mean retinal sensitivity, whereas gender, age and duration of disease had no effect on visual function.

Interestingly, Querques et al note that retinal sensitivity was significantly poorer in patients with Type 2 than in those with Type 1 diabetes, which they hypothesise could be attributed to the occurrence of systemic hypertension, recorded in 14 and zero patients with Type 2 and Type 1 diabetes, respectively.

They conclude in Retina: “We demonstrated a significantly reduced sensitivity in both nonproliferative diabetic retinopathy groups without diabetic macular edema compared with healthy controls.”

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